I'm not quite sure where to put this as there seems to be two threads about rock art and haven't managed to read them all yet.

I picked up a library book the other day by Frank Delaney called 'Ireland'. From what I can make out it is the history of Ireland as told by a travelling story teller in the 1950s. He pitches up one night looking for food and shelter. As the family who take him and their neighbours gather around the fire he tells the story of how Newgrange was built (the opening chapter of the book). Fictional of course but quite fascinating:

"Here and there he stopped to caress the shapes. He stroked the stern triangles and merry whorls, geometric chevrons that looked like worried frowns, smiling triskelia and swirls, a little rippling field of diamond patterns, sweet presences on and in stone. They reflected the world around Newgrange: the triangles made by the hilltops in certain phases of light; the rings on a tree's trunk; the eddies and whirls of the river Boyne."